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Well I used a brass plumbing fitting for a "drill bushing". In the iron mold , I was counting on the crush fit effect when I closed the two halves up around it. The thru hole size on the fitting was 0.185" so, 3/16" was the was to go. And pins are plentiful with "dead" drill bits handy.
I think a steel drill bushing would be nice but, if it turned in an aluminum mold while it was being drilled, could be big mess. Drill bushings in bronze are a little more forgiving, although the commercial sizing is expensive. The plumbing fitting was free and I cheaped out on mine.

Seems to me you could eliminate the need for a bushing pretty easily. Use a drill rod, wrapped in tape if necessary, to set the center. Clamp the work piece to the table (with the rod still in the cavity), then swap out the drill rod for your through drill.

Seems to me you could eliminate the need for a bushing pretty easily. Use a drill rod, wrapped in tape if necessary, to set the center. Clamp the work piece to the table (with the rod still in the cavity), then swap out the drill rod for your through drill.

From years and years of using drill bushings, they MAKE the drill go where it is supposed to, the drill will bend and flex if need be but still go where it is supposed to go. It takes a LOT better machine and setup to drill a hole without a guide bushing.

Nice work you guys. I suppose it would be just as easy to make a second pin
for a flat nose, so you could cast either style. Wife just got a LCP 380,
might be nice to cast HPs for that, but that's the mold I use for cores for swaging.